PhD Oral Exam - Mouna Nakkar, Information Systems Engineering

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Edge computing (EC) is one of the most promising decentralized network paradigms in the proliferation era of the Internet of Things (IoT). Although this paradigm has high potential in terms of performance and de-centralization, it carries several security concerns. One of the most important security properties for the EC paradigm is authenticity. It allows different edge computing entities to verify each other through cryptographic means. Additionally, authenticity regulates access control to different edge computing resources and data. There are several types of authentications, one-way authentication, mutual authentication, broadcast authentication, group authentication, and others. In our thesis, we focus on designing security protocols for different edge computing applications that require either mutual authentication, broadcast authentication, or group authentication. In all our proposed protocols we utilize lightweight security primitives suitable for the three-tier cloud-edge-IoT architecture.

In the first protocol, we utilize lightweight cryptographic primitives to design mutual authentication for EC broadcast messages. Specifically, the used primitives are only hash-based one-way chain, symmetric-key cryptography, and a hash function. The protocol establishes key-agreement for group and individual nodes in each session. The achieved security properties for our protocol are mutual-authentication for broadcast messages, message secrecy, message integrity, and forward secrecy. We formally define and prove the main security properties of our protocol theoretically using the indistinguishability game. We compare our protocol to other lightweight protocols in terms of security and performance to prove its advantages in terms of computations, communication overhead, and storage.

Motivated by the fact that mass authentication is one of the desirable security features in the edge computing paradigm, our second proposed protocol is a lightweight group authentication scheme (GAS) with session key-agreement. The protocol utilizes lightweight cryptographic primitives, namely, Shamir’s secret sharing (SSS) scheme and aggregated message authentication code (Aggregated-MAC). Unlike other group authentication schemes, our protocol provides multiple asynchronous authentications. Furthermore, we implement a simple key refreshing mechanism such that in each session, a new session-key between group nodes and the authenticating server is established without the need for redistributing new shares. Our security analysis includes proving that our protocol provides group authenticity, message forward secrecy, and prevents several attacks.

Extending our group authentication design, our third security protocol is a flexible GAS based on Physical Unclonable Function (PUF) and Shamir’s secret sharing scheme. Specifically, we apply PUFs on SSS and utilize the SSS-homomorphic property to achieve multiple-time group authentications with the same set of shares. Our scheme is lightweight, establishes a new group key-agreement per session, and supports efficient node-evicting mechanism. Furthermore, in our protocol, the group nodes do not store any shares; instead, the nodes derive their secret-shares from their PUF-responses. We formally analyze our protocol theoretically and with automated tools, Automated Validation of Internet Security Protocol and Applications (AVISPA), to prove that our scheme achieves message secrecy and authenticity.

Finally, we propose a lightweight symmetric-key based protocol which provides edge-IoT mutual authentication, forward secrecy, backward secrecy, and anonymity. The security primitives used in our fourth protocol are pseudo-random function (PRF), random number generation, a hash function, and xor. We prove the security goals of the protocol and compare it to other lightweight authentication protocols.